This application is based on and incorporates herein by reference Japanese Patent Application No. 2001-155605 filed May 24, 2001.
The present invention relates to an on-board control system and method, which ensures control operation in a vehicle.
It is proposed to design a control system equipped on a vehicle to memorize data of the event of collision of the vehicle in a collision memory circuit and unlock the doors of the vehicle in accordance with the collision data in the collision memory circuit. Even if the power voltage falls (or fails) temporarily due to the impact of collision, this control system is capable of unlocking the doors promptly immediately after the power voltage recovers based on the collision data stored at the occurrence of collision.
The on-board control system has a voltage holding capacitor connected to the power line so that the fall of line voltage slows at the momentary power failure, allowing the collision data storing operation. In order to have a voltage hold time that is long enough to store the collision data in the memory circuit, the voltage holding capacitor must have a large capacitance, which adds costs.
Temporary power voltage fall or power failure may be caused by the vibration of the vehicle, cranking of the engine, and breakage of the power line. Control operations will be suspended in these cases.
The present invention has an object to provide an on-board control system and method which is designed, without the need of cost increase, to operate stably at a temporary fall of power voltage.
An on-board control system according to the present invention determines a fall, or drop of power voltage which is caused by the collision of a vehicle, vibration of the vehicle, or cranking of a vehicle engine. The control system then stops one of several control operations selectively at the fall of power voltage, so that the control system has its load current reduced, thereby slowing the voltage fall. Accordingly, the control system can slow the voltage fall without requiring a voltage holding capacitor with a large capacitance connected to the power line. The control system can perform the critical operations before the power voltage falls to the voltage level at which the microcomputer, etc. is reset. Therefore, the control system can operate stably at a fall of power voltage without the need of cost increase for a large capacitor. The control system has the enhanced reliability against the momentary power failure of the vehicle.